JP3852398B2 - Translucent ceramics and optical components and optical elements using the same - Google Patents

Description

【００３１】
表１に示す試料のうち、高い直線透過率が得られた試料３５について、紫外から赤外の波長帯（λ＝２００〜１００００ｎｍ）における直線透過率を測定した。なお、赤外領域での直線透過率の測定には、ニコレー社製分光光度計（ＦＴ−ＩＲ Ｍａｇｎａ７５０）を用いた。この直線透過率の測定結果を図２（ａ）（ｂ）に示す。同図から、試料３５は直線透過率において波長依存性を有することが分かる。
【００３２】
また、同じく試料３５について、ＴＥモードにおける屈折率を測定した結果を図３に示す。さらに、試料３５について、λ＝６３３ｎｍ、１３００ｎｍ、１５５０ｎｍのそれぞれにおけるＴＥモードおよびＴＭモードでの屈折率を測定した結果を表２に示す。表２において、ＴＥモードおよびＴＭモードでの屈折率が同じ値であることから、複屈折が生じていないことが分かる。
【００３３】
【表２】

【００３４】
ここで、試料３５の直線透過率は７５．８％であり、屈折率は２．０７４であった。一般に、直線透過率の測定においては、空気中から試料に対して垂直に光が入射する。このため、例えば、屈折率（ｎ）が２．０７４である場合、Ｆｒｅｓｎｅｌの法則より、試料表面での反射率と裏面での反射率の合計は２３．１％となる。よって、屈折率が２．０７４である試料の直線透過率の理論最大値は、７６．９％となる。試料３５において、直線透過率は７５．８％であるから、理論値に対する相対透過率は９８．５％となる。これは、焼結体内部での透過損失がほとんどないことを示している。したがって、試料３５の表面に反射防止膜（ＡＲ膜＝Ａｎｔｉ−Ｒｅｆｌｅｃｔｉｏｎ膜）を形成すれば、得られる直線透過率をほぼ理論値とすることができる。このように、本発明の組成を有する透光性セラミックスは、光学素子として利用可能な優れた特性を有するものである。
【００３５】
また、表１の試料のうち、高い直線透過率が得られた他の試料３４に対して、比較例として、鋳込み成形による２インチ角の成形体を１６００℃で焼成して焼結体を得た。表３は、この試料３４と比較例の直線透過率および屈折率を対比したものである。表３において、両者の直線透過率および屈折率は、互いに同等の値である。このように、本発明の組成を有する透光性セラミックスによれば、成形法に関わらず高い直線透過率および屈折率が得られるものである。
【００３６】
【表３】

【００３７】
また、上記実施例と焼成温度が異なる試料について、直線透過率および屈折率を測定した結果を表１に併せて示す。これらの試料は、上記実施例と同じ原料を用い、同じ条件で混合、仮焼、粉砕、乾燥および造粒を行い、得られた粉末を円板状に成形し、この成形体を最高温度域１６５０℃で焼成したものである。１６５０℃で焼成した試料の中には、１６００℃で焼成した試料に比べて、直線透過率の値が良好なものが見られる。
【００３８】
図１は、本発明の透光性セラミックスの組成である一般式Ｂａ｛（Ｓｎ_uＺｒ_1-u）_xＭｇ_yＴａ_z｝_vＯ_w（但し、ｘ＋ｙ＋ｚ＝１，０≦ｕ≦１，１≦ｖ≦１．０５，ｗは任意の数）におけるｘ、ｙ、ｚの組成範囲を示す三元図である。
【００３９】
同図において、Ａ、Ｂ、Ｃ、Ｄの各点を結んだ四角形ＡＢＣＤで囲まれた領域（境界線ＡＢ上は含まない。）が、本発明の透光性セラミックスの組成範囲である。この組成を有する焼結体は、直線透過率が２０％以上となり、屈折率は２．０７前後の高い値となる。さらに、Ｅ、Ｆ、Ｇ、Ｈの各点を結んだ四角形ＥＦＧＨで囲まれた領域の組成を有する焼結体では、直線透過率が５０％以上となり、屈折率は同じく２．０７前後の高い値となる。
【００４０】
また、表１における試料番号の一部を図１上に示した。図１において、試料番号に＊印を付したものは、表１においても同じ印が付された、本発明の範囲外の試料である。
【００４１】
【実施例２】
この実施例２は、一般式Ｂａ｛（Ｓｎ_uＺｒ_1-u）_xＭｇ_yＴａ_z｝_vＯ_wで表され、この一般式のｘ，ｙ，ｚが図１に示す三元図における各点Ｅ，Ｆ，Ｇ，Ｈを結んだ四角形ＥＦＧＨで囲まれた領域内にある組成を有する主成分に、微量の酸化物を添加したものである。ここでは、微量の酸化物を添加することにより、直線透過率および屈折率を変化させた。
【００４２】
主成分としては、実施例１における表１の試料２６を用いた。実施例１と同様に、高純度のＢａＣＯ₃，ＳｎＯ₂，ＺｒＯ₂，ＭｇＣＯ₃およびＴａ₂Ｏ₅を準備した。表１の試料２６と同じ組成が得られるように、各原料を秤量した。また、微量の酸化物として、Ａｌ₂Ｏ₃，Ｙ₂Ｏ₃，ＣｕＯ，ＴｉＯ₂，Ｇａ₂Ｏ₃，ＷＯ₃，Ｌａ₂Ｏ₃，Ｓｍ₂Ｏ₃，Ｅｕ₂Ｏ₃，Ｎｄ₂Ｏ₃，Ｇｄ₂Ｏ₃，Ｄｙ₂Ｏ₃，Ｈｏ₂Ｏ₃，Ｙｂ₂Ｏ₃，Ｅｒ₂Ｏ₃，Ｌｉ₂ＣＯ₃，ＢａＴｉＯ₃ を準備し、主成分に対する添加量が表４、表５のとおりになるように秤量した。なお、Ｌｉ₂ＣＯ₃については、Ｌｉ₂Ｏに換算した添加量となっている。このように秤量した主成分原料および添加物原料を混合した。そして、実施例１と同じ要領で仮焼、粉砕、焼成したものを鏡面加工して透光性セラミックスの試料を得た。
【００４３】
上記試料のそれぞれについて、可視光領域（λ＝６３３ｎｍ）における直線透過率および屈折率を測定した。この測定結果を表４、表５に示す。表４、表５において、試料番号に＊印を付したものは本発明の範囲外のものであり、いずれも直線透過率が２０％未満のものである。
【００４４】
【表４】

【００４５】
【表５】

【００４６】
表４、表５と表１の各値を比較すると、各酸化物の添加量に応じて直線透過率および屈折率が増減することが分かる。ここで、一般に、光学部品においては、用途に応じて特性が細分化されており、屈折率については、小数点以下第５位の値までの精度が要求されることが多い。表１と表４、表５とで、屈折率は、小数点以下第３位において異なる値となっており、光学部品として明確に異なる特性を有するものと言える。
【００４７】
このように、酸化物の添加の有無を選択したり、添加量を調整したりすることにより、光学部品としての用途に応じて異なる特性の透光性セラミックスを得ることができる。
【００４８】
また、表４の試料７および表５の試料９２について、それぞれ、λ＝６３３ｎｍにおけるＴＥモードおよびＴＭモードでの屈折率を測定した。その結果を表６に示す。表６において、ＴＥモードおよびＴＭモードでの屈折率が同じ値であることから、複屈折が生じていないことが分かる。
【００４９】
【表６】

【００５０】
【実施例３】
上述のように、実施例１，２にかかる透光性セラミックスは、直線透過率および屈折率において高い値を示し、複屈折も生じないため、光学部品への利用が望める。例えば、図４に示すような両凸レンズ１０、または両凹レンズ１１、あるいは光路長調整板１２、さらには球状レンズ１３等の素材として好適である。
【００５１】
このような光学部品を搭載した光学素子として、光ピックアップを例に取り、説明する。
【００５２】
光ピックアップは、図５に示すように、コンパクトディスクやミニディスクといった記録媒体１に対して、コヒーレントな光であるレーザ光を照射し、その反射光から記録媒体１に記録された情報を再生するものである。
【００５３】
このような光ピックアップにおいては、光源としての半導体レーザ素子５からのレーザ光を平行光に変換するコリメータレンズ４が設けられ、その平行光の光路上にハーフミラー３が設けられている。このハーフミラー３は、コリメータレンズ４からの入射光は通して直進させるが、記録媒体１からの反射光については、反射光の進行方向を例えば約９０度の反射により変更するものである。
【００５４】
また、光ピックアップには、ハーフミラー３からの入射光を記録媒体１の記録面上に集光するための対物レンズ２が設けられている。この対物レンズ２は、記録媒体１からの反射光を効率よくハーフミラー３に対して出射するものでもある。反射光が入射されたハーフミラー３では、反射により位相が変化することで、上記反射光の進行方向が変更される。
【００５５】
さらに、光ピックアップには、変更された反射光を集光するための集光レンズ６が設けられている。そして、反射光の集光位置に、反射光から情報を再生するための受光素子７が設けられている。
【００５６】
このように構成される光ピックアップにおいて、対物レンズ２の素材として、本発明にかかる透光性セラミックスを用いることができる。この透光性セラミックスは屈折率が大きいため、光ピックアップの小型化や薄型化が可能であり、開口を増加させることができる。
【００５７】
なお、本実施例においては、本発明の透光性セラミックスを対物レンズ２に用いた場合について説明したが、他の光学部品、例えば、コリメータレンズ４または集光レンズ６、あるいはハーフミラー３に用いることもできる。
【００５８】
また、本発明は、上記各実施例に限定されるものではなく、特許請求の範囲内で適宜、変更を加えることができる。例えば、原料の形態は酸化物もしくは炭酸塩に限定されるものではなく、焼結体とした段階で所望の特性が得られる原料であればよい。また、焼成雰囲気について、上記実施例の約９８％という酸素濃度の値は、使用した実験設備の条件下において最も好ましい値である。この条件下においては、９０％以上の酸素濃度が確保できれば、所望の特性を備えた焼結体が得られる。
【００５９】
【発明の効果】
本発明の透光性セラミックスは、常誘電体であり、かつ多結晶体であるため、複屈折を生じない。したがって、レンズ等の光学部品に容易に適用できる。
【００６０】
また、本発明の透光性セラミックスは、２０％以上さらには５０％以上の高い直線透過率と２．０以上の高い屈折率を有する。このため、比較的小さな外形寸法で所望の光学特性を発揮することができる。
【００６１】
さらに、本発明の透光性セラミックスは、可視光領域から赤外領域までの光を透過するため、広範囲での利用が可能である。
【００６２】
また、本発明の透光性セラミックスは、主成分に対して酸化物を添加することにより、光学部品としての用途に応じて、直線透過率および屈折率を変化させることが可能である。
【００６３】
本発明の光学素子においては、上述の高い光学特性を有する透光性セラミックスが光学部品として用いられているため、光学素子の小型化、薄型化を実現することができる。
【図面の簡単な説明】
【図１】本発明の透光性セラミックスの組成範囲を示す三元図である。
【図２】（ａ）（ｂ）とも、本発明の透光性セラミックスの直線透過率の波長依存性を示すグラフである。
【図３】本発明の透光性セラミックスの屈折率を示すグラフである。
【図４】本発明の透光性セラミックスからなる光学部品の説明図であり、（ａ）は両凸レンズを示し、（ｂ）は両凹レンズを示し、（ｃ）は光路長調整板を示し、（ｄ）は球状レンズを示す。
【図５】本発明の透光性セラミックスからなる光学部品を搭載した光学素子の一実施例（光ピックアップ）を示す説明図である。
【符号の説明】
２ 対物レンズ（光学部品）
１０ 両凸レンズ（光学部品）
１１ 両凹レンズ（光学部品）
１２ 光路長調整板（光学部品）
１３ 球状レンズ（光学部品）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a translucent ceramic that is a paraelectric material having a high refractive index and a high light transmittance and is useful as an optical component, and an optical element using the same.
[0002]
[Prior art]
Conventionally, glass, plastic, or single crystal such as lithium niobate (LiNbO ₃ ) has been used as an optical component material mounted on an optical element such as an optical pickup.
[0003]
Glass and plastic are used for optical components such as lenses because they have high light transmittance and can be easily processed into a desired shape. A single crystal of LiNbO ₃ is used for optical parts such as an optical waveguide by utilizing its electrochemical characteristics and birefringence. Optical elements such as optical pickups using such optical components are required to be further reduced in size and thickness. (For example, see Patent Documents 1 and 2.)
[0004]
[Patent Document 1]
JP-A-5-107467 (all pages, all figures)
[Patent Document 2]
Japanese Patent Laid-Open No. 7-244865 (Claim 6, paragraph number 0024)
[0005]
[Problems to be solved by the invention]
Since the above-described conventional glass and plastic have a refractive index of less than 1.9, there is a limit to miniaturization and thickness reduction in optical components and optical elements using them. In addition, plastic has a hygroscopic property, and also has a low refractive index and birefringence, and thus has a problem in efficiently transmitting and collecting incident light. Furthermore, although a single crystal such as LiNbO ₃ has a high refractive index (n = 2.3), it generates birefringence, so it cannot be used for optical parts such as lenses, and its application is limited.
[0006]
Therefore, an object of the present invention is to provide a translucent ceramic excellent in optical characteristics that does not cause birefringence and an optical element using the same.
[0007]
[Means for Solving the Problems]
Present first invention can be represented by the general formula _{Ba {(Sn u Zr 1-} u) x Mg y Ta z} v O w ( provided that, x + y + z = 1,0 ≦ u ≦ 1,1 ≦ v ≦ 1.05, w Is an arbitrary number), and x, y, z in the above general formula are points A (0.4, 0.23, 0.37), B (0, 0.39, 0.61), C (0, 0.27, 0.73), D (0.4, 0.11, 0.49) in the region surrounded by the rectangle ABCD (boundary line) The translucent ceramic is characterized in that the main component is a composition (not included on AB) , the refractive index is 2.0 or more, and the linear transmittance is 20% or more .
[0009]
Present second invention, the general formula _{Ba {(Sn u Zr 1-} u) x Mg y Ta z} v O w ( provided that, x + y + z = 1,0 ≦ u ≦ 1,1 ≦ v ≦ 1.05, w Is an arbitrary number), and x, y, and z in the general formula are points E (0.4, 0.21, 0.39) and F (0. 125, 0.325, 0.55), G (0.125, 0.29, 0.585), and a region surrounded by a rectangle EFGH connecting H (0.4, 0.17, 0.43) The translucent ceramic is characterized by having a composition contained therein as a main component , a refractive index of 2.0 or more, and a linear transmittance of 50% or more .
[0011]
According to the third aspect of the present invention, in the second aspect of the present invention, Al ₂ O ₃ , Y ₂ O ₃ , CuO, TiO ₂ , Ga ₂ O ₃ , WO ₃ , La ₂ O ₃ , Sm with respect to the main component. 1 mol of at least one oxide selected from ₂ O ₃ , Eu ₂ O ₃ , Nd ₂ O ₃ , Gd ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Yb ₂ O ₃ , Er ₂ O ₃ % Or less is added.
[0012]
The fourth invention of the present application is the translucent ceramic according to the second invention, wherein 2 mol% or less of Li ₂ O or BaTiO ₃ is added to the main component.
[0013]
The fifth invention is a translucent ceramic according to any one of the first to fourth inventions, which is a paraelectric material and a polycrystalline material.
[0014]
The sixth invention is an optical component comprising the translucent ceramic according to any one of the first to fifth inventions.
[0015]
The seventh invention is an optical element in which the optical component according to the sixth invention is mounted.
[0016]
Here, the paraelectric material has a characteristic that the dielectric constant does not change even when an electric field is applied. Since the translucent ceramic of the present invention is a paraelectric material and a polycrystalline material, birefringence does not occur. Therefore, it can be easily applied to optical components such as lenses.
[0017]
The translucent ceramic of the present invention has a high linear transmittance of 20% or more or 50% or more and a high refractive index of 2.0 or more. For this reason, desired optical characteristics can be exhibited with a relatively small external dimension.
[0018]
Moreover, since the translucent ceramic of this invention permeate | transmits the light from visible region to an infrared region, it can be utilized in a wide range.
[0019]
Moreover, the translucent ceramics of this invention can change a linear transmittance | permeability and a refractive index according to the use as an optical component by adding an oxide with respect to a main component.
[0020]
Furthermore, in the optical element of the present invention, the above-described translucent ceramic having high optical characteristics is used as an optical component, so that the optical element can be reduced in size and thickness.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
[0022]
[Example 1]
A procedure for producing the translucent ceramic of the present invention will be described.
[0023]
First, high purity BaCO ₃ , SnO ₂ , ZrO ₂ , MgCO ₃ and Ta ₂ O ₅ were prepared as raw materials. Then, (the w arbitrary number) formula _{Ba {(Sn u Zr 1-} u) x Mg y Ta z} v O w represented by, so that each sample shown in Table 1 are obtained, the raw materials Weighed and wet mixed in a ball mill for 16 hours. This mixture was dried and then calcined at 1300 ° C. for 3 hours to obtain a calcined product. Note that the value of w was approximately 3 after calcination.
[0024]
This calcined product was placed in a ball mill together with water and an organic binder, and wet pulverized for 16 hours. For example, ethyl cellulose is used as the organic binder. Other than ethyl cellulose, it has a function as a binder for ceramic molded bodies and reacts with oxygen in the atmosphere at, for example, about 500 ° C. before it reaches the sintering temperature in the sintering process. As long as it disappears as a result, it can be used as an organic binder.
[0025]
After the pulverized product is dried, it is granulated through a 50-mesh net (sieving), and the resulting powder is pressed at a pressure of 2000 kg / cm ² to form a disk-shaped product having a diameter of 30 mm and a thickness of 2 mm. Got the body.
[0026]
Next, the molded body was embedded in the same composition powder. Here, the same composition powder is obtained by calcining and pulverizing a raw material prepared so as to have the same composition as the molded body. With this same composition powder, it is possible to suppress volatilization of the volatile components in the molded body during firing. The same composition powder preferably has the same composition as that of the molded body, but may not have the same composition as long as it is an equivalent composition system. Moreover, it does not necessarily need to have translucency.
[0027]
The molded body embedded in the same composition powder was put into a firing furnace and heated in an air atmosphere to remove the binder. Subsequently, oxygen was injected into the furnace while raising the temperature, and the oxygen concentration in the firing atmosphere was increased to about 98% at the maximum temperature range of 1600 ° C. or 1650 ° C. The fired temperature and oxygen concentration were maintained, and the molded product was fired for 20 hours to obtain a sintered body. The total pressure during firing was 1 atm or less.
[0028]
The sintered body thus obtained was mirror-finished and finished into a disk shape having a thickness of 0.4 mm to obtain a sample of translucent ceramics.
[0029]
For each of the above samples, the linear transmittance and refractive index in the visible light region (λ = 633 nm) were measured. A Shimadzu spectrophotometer (UV-200S) was used for the measurement of the linear transmittance. In addition, a prism coupler (MODEL 2010) manufactured by Metricon was used for the measurement of the refractive index. The measurement results are shown in Table 1. In Table 1, those marked with * in the sample numbers are outside the scope of the present invention, and all are unsintered or have a linear transmittance of less than 20%.
[0030]
[Table 1]

[0031]
Among the samples shown in Table 1, the linear transmittance in the ultraviolet to infrared wavelength band (λ = 200 to 10,000 nm) was measured for sample 35 in which high linear transmittance was obtained. Note that a spectrophotometer (FT-IR Magna 750) manufactured by Nicorey was used for the measurement of the linear transmittance in the infrared region. The measurement results of the linear transmittance are shown in FIGS. From the figure, it can be seen that the sample 35 has wavelength dependency in the linear transmittance.
[0032]
Moreover, the result of having measured the refractive index in TE mode similarly about the sample 35 is shown in FIG. Further, Table 2 shows the results of measuring the refractive index in the TE mode and TM mode at λ = 633 nm, 1300 nm, and 1550 nm for the sample 35, respectively. In Table 2, it can be seen that birefringence does not occur because the refractive index in the TE mode and the TM mode are the same value.
[0033]
[Table 2]

[0034]
Here, the linear transmittance of the sample 35 was 75.8%, and the refractive index was 2.074. In general, in the measurement of the linear transmittance, light enters perpendicularly from the air to the sample. Therefore, for example, when the refractive index (n) is 2.074, the total of the reflectance on the sample surface and the reflectance on the back surface is 23.1% according to Fresnel's law. Therefore, the theoretical maximum value of the linear transmittance of a sample having a refractive index of 2.074 is 76.9%. In the sample 35, since the linear transmittance is 75.8%, the relative transmittance with respect to the theoretical value is 98.5%. This indicates that there is almost no transmission loss inside the sintered body. Therefore, if an antireflection film (AR film = Anti-Reflection film) is formed on the surface of the sample 35, the obtained linear transmittance can be made almost the theoretical value. As described above, the translucent ceramic having the composition of the present invention has excellent characteristics that can be used as an optical element.
[0035]
Further, among the samples in Table 1, as a comparative example, another sample 34 having a high linear transmittance was fired at 1600 ° C. to obtain a sintered body by firing a 2 inch square molded body by casting. It was. Table 3 compares the linear transmittance and refractive index of the sample 34 and the comparative example. In Table 3, the linear transmittance and refractive index of both are equivalent values. Thus, according to the translucent ceramics having the composition of the present invention, high linear transmittance and refractive index can be obtained regardless of the forming method.
[0036]
[Table 3]

[0037]
Table 1 also shows the results of measuring the linear transmittance and the refractive index of samples having different firing temperatures from the above examples. These samples were mixed, calcined, pulverized, dried and granulated under the same conditions using the same raw materials as in the above examples, and the obtained powder was formed into a disk shape. Baked at 1650 ° C. Among the samples fired at 1650 ° C., a sample having a good linear transmittance is seen as compared with the sample fired at 1600 ° C.
[0038]
Figure 1 is a composition of translucent ceramic of the present invention the general formula _{Ba {(Sn u Zr 1-} u) x Mg y Ta z} v O w ( provided that, x + y + z = 1,0 ≦ u ≦ 1,1 It is a ternary diagram showing the composition range of x, y, z in ≦ v ≦ 1.05, w is an arbitrary number).
[0039]
In the figure, a region surrounded by a rectangle ABCD connecting points A, B, C, and D (not including the boundary line AB) is the composition range of the translucent ceramic of the present invention. The sintered body having this composition has a linear transmittance of 20% or more and a refractive index of about 2.07. Furthermore, in the sintered body having the composition of the region surrounded by the square EFGH connecting the points E, F, G, and H, the linear transmittance is 50% or more, and the refractive index is also high, around 2.07. Value.
[0040]
A part of the sample numbers in Table 1 is shown in FIG. In FIG. 1, the sample number marked with * is a sample outside the scope of the present invention, which is also marked with the same mark in Table 1.
[0041]
[Example 2]
This Example 2 is represented by the general formula Ba {(Sn _u Zr _1-u ) _x Mg _y Ta _z } _v O _w , and x, y, and z of this general formula are shown in the ternary diagram shown in FIG. A small amount of oxide is added to a main component having a composition in a region surrounded by a square EFGH connecting points E, F, G, and H. Here, the linear transmittance and refractive index were changed by adding a small amount of oxide.
[0042]
As the main component, the sample 26 of Table 1 in Example 1 was used. As in Example 1, high-purity BaCO ₃ , SnO ₂ , ZrO ₂ , MgCO ₃ and Ta ₂ O ₅ were prepared. Each raw material was weighed so that the same composition as sample 26 in Table 1 was obtained. Further, as trace amounts of oxides, Al ₂ O ₃ , Y ₂ O ₃ , CuO, TiO ₂ , Ga ₂ O ₃ , WO ₃ , La ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Nd ₂ O ₃ , Gd ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Yb ₂ O ₃ , Er ₂ O ₃ , Li ₂ CO ₃ , BaTiO ₃ are prepared, and the addition amount with respect to the main component is as shown in Tables 4 and 5 Weighed so that Note that the Li ₂ CO _3, has a amount in terms of Li ₂ O. The main component raw material and additive raw material thus weighed were mixed. Then, a sample of translucent ceramics was obtained by mirror finishing the calcination, pulverization, and firing in the same manner as in Example 1.
[0043]
For each of the above samples, the linear transmittance and refractive index in the visible light region (λ = 633 nm) were measured. The measurement results are shown in Tables 4 and 5. In Tables 4 and 5, the sample numbers marked with * are outside the scope of the present invention, and both have a linear transmittance of less than 20%.
[0044]
[Table 4]

[0045]
[Table 5]

[0046]
Comparing the values in Table 4, Table 5, and Table 1, it can be seen that the linear transmittance and refractive index increase or decrease depending on the amount of each oxide added. Here, in general, the characteristics of optical components are subdivided according to applications, and the refractive index is often required to be accurate to the fifth decimal place. In Table 1, Table 4, and Table 5, the refractive index has a different value in the third place after the decimal point, and it can be said that the optical component has clearly different characteristics.
[0047]
Thus, by selecting whether or not an oxide is added or adjusting the amount added, translucent ceramics having different characteristics can be obtained depending on the use as an optical component.
[0048]
Moreover, the refractive index in TE mode and TM mode in (lambda) = 633nm was measured about the sample 7 of Table 4, and the sample 92 of Table 5, respectively. The results are shown in Table 6. In Table 6, it can be seen that birefringence does not occur since the refractive indexes in the TE mode and the TM mode have the same value.
[0049]
[Table 6]

[0050]
[Example 3]
As described above, the translucent ceramics according to Examples 1 and 2 show high values in linear transmittance and refractive index, and birefringence does not occur. For example, it is suitable as a material for the biconvex lens 10, the biconcave lens 11, the optical path length adjusting plate 12, and the spherical lens 13 as shown in FIG.
[0051]
An optical pickup will be described as an example of an optical element on which such an optical component is mounted.
[0052]
As shown in FIG. 5, the optical pickup irradiates a recording medium 1 such as a compact disc or a minidisc with laser light, which is coherent light, and reproduces information recorded on the recording medium 1 from the reflected light. Is.
[0053]
In such an optical pickup, a collimator lens 4 for converting laser light from a semiconductor laser element 5 as a light source into parallel light is provided, and a half mirror 3 is provided on the optical path of the parallel light. The half mirror 3 allows the incident light from the collimator lens 4 to pass straight, but the reflected light from the recording medium 1 changes the traveling direction of the reflected light by, for example, reflection of about 90 degrees.
[0054]
Further, the optical pickup is provided with an objective lens 2 for condensing incident light from the half mirror 3 on the recording surface of the recording medium 1. The objective lens 2 also emits reflected light from the recording medium 1 to the half mirror 3 efficiently. In the half mirror 3 on which the reflected light is incident, the traveling direction of the reflected light is changed by changing the phase by reflection.
[0055]
Further, the optical pickup is provided with a condensing lens 6 for condensing the changed reflected light. And the light receiving element 7 for reproducing | regenerating information from reflected light is provided in the condensing position of reflected light.
[0056]
In the optical pickup configured as described above, the translucent ceramic according to the present invention can be used as the material of the objective lens 2. Since this translucent ceramic has a high refractive index, it is possible to reduce the size and thickness of the optical pickup and increase the opening.
[0057]
In the present embodiment, the case where the translucent ceramic of the present invention is used for the objective lens 2 has been described. You can also.
[0058]
Further, the present invention is not limited to the above embodiments, and can be appropriately modified within the scope of the claims. For example, the form of the raw material is not limited to oxides or carbonates, and any raw material can be used as long as desired characteristics can be obtained at the stage of forming a sintered body. In addition, for the firing atmosphere, an oxygen concentration value of about 98% in the above example is the most preferred value under the conditions of the experimental equipment used. Under this condition, if an oxygen concentration of 90% or more can be secured, a sintered body having desired characteristics can be obtained.
[0059]
【The invention's effect】
Since the translucent ceramic of the present invention is a paraelectric material and a polycrystalline material, birefringence does not occur. Therefore, it can be easily applied to optical components such as lenses.
[0060]
The translucent ceramic of the present invention has a high linear transmittance of 20% or more, further 50% or more, and a high refractive index of 2.0 or more. For this reason, desired optical characteristics can be exhibited with a relatively small external dimension.
[0061]
Furthermore, since the translucent ceramic of the present invention transmits light from the visible light region to the infrared region, it can be used in a wide range.
[0062]
Moreover, the translucent ceramics of this invention can change a linear transmittance and a refractive index according to the use as an optical component by adding an oxide with respect to a main component.
[0063]
In the optical element of the present invention, the above-described translucent ceramic having high optical characteristics is used as an optical component, so that the optical element can be reduced in size and thickness.
[Brief description of the drawings]
FIG. 1 is a ternary diagram showing a composition range of a translucent ceramic of the present invention.
FIGS. 2A and 2B are graphs showing the wavelength dependence of the linear transmittance of the translucent ceramic of the present invention.
FIG. 3 is a graph showing the refractive index of the translucent ceramic of the present invention.
FIG. 4 is an explanatory view of an optical component made of a translucent ceramic of the present invention, (a) shows a biconvex lens, (b) shows a biconcave lens, (c) shows an optical path length adjusting plate, (D) shows a spherical lens.
FIG. 5 is an explanatory view showing an example (optical pickup) of an optical element on which an optical component made of a translucent ceramic of the present invention is mounted.
[Explanation of symbols]
2 Objective lens (optical component)
10 Biconvex lens (optical component)
11 Biconcave lens (optical component)
12 Optical path length adjustment plate (optical component)
13 Spherical lens (optical component)

Claims (7)

Table by formula _{Ba {(Sn u Zr 1-} u) x Mg y Ta z} v O w ( provided that, x + y + z = 1,0 ≦ u ≦ 1,1 ≦ v ≦ 1.05, w is an arbitrary number) And
In the ternary diagram shown in FIG. 1, x, y, and z in the general formula are points A (0.4, 0.23, 0.37), B (0, 0.39, 0.61), Composition in a region surrounded by a rectangle ABCD connecting C (0, 0.27, 0.73) and D (0.4, 0.11, 0.49) (not including the boundary line AB) As the main component ,
Furthermore, the translucent ceramics characterized by having a refractive index of 2.0 or more and a linear transmittance of 20% or more . Table by formula _{Ba {(Sn u Zr 1-} u) x Mg y Ta z} v O w ( provided that, x + y + z = 1,0 ≦ u ≦ 1,1 ≦ v ≦ 1.05, w is an arbitrary number) And
In the ternary diagram shown in FIG. 1, x, y, and z in the general formula are points E (0.4, 0.21, 0.39) and F (0.125, 0.325, 0.55). ), G (0.125,0.29,0.585), H a composition is in a region surrounded by the rectangle EFGH for connecting (0.4,0.17,0.43) as a main component ,
Furthermore, the translucent ceramics characterized by having a refractive index of 2.0 or more and a linear transmittance of 50% or more . With respect to the main component, Al ₂ O ₃ , Y ₂ O ₃ , CuO, TiO ₂ , Ga ₂ O ₃ , WO ₃ , La ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Nd ₂ O ₃ , The oxide according to claim 1, wherein at least one oxide selected from Gd ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Yb ₂ O ₃ and Er ₂ O ₃ is added in an amount of 1 mol% or less. 2. The translucent ceramic according to 2. The translucent ceramic according to claim 2 , wherein 2 mol% or less of Li ₂ O or BaTiO ₃ is added to the main component. Paraelectric a body and the translucent ceramics according to any one of claims 1 to 4, characterized in that a polycrystal. An optical component comprising the translucent ceramic according to any one of claims 1 to 5 . An optical element on which the optical component according to claim 6 is mounted.

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